Paper is a network of crossing fibers, more or less bonded to each other. Loose ends from some of these fibers project above the surface of the paper. As the paper proceeds through different machinery some of these fibers are pulled free, producing what is known in the industry as fuzz, dust, or lint.
Saturating kraft is a special type of absorbent paper used primarily for the core stock of decorative laminates. Fuzz released from saturating kraft has traditionally been a major problem for laminate producers. During the production of laminates, saturating kraft paper passes through a phenolic resin bath which makes the paper extremely sticky. Since loose fuzz has a tendency to agglomerate and form fuzz balls, it is common for some of these fuzz balls to collect on and stick to the resin-treated paper. As the paper proceeds through the drying process and becomes cut, sandwiched, and pressed into finished laminates, adhering fuzz balls can cause surface imperfections known as pressure marks. Because pressure-marked laminates are unsuitable for commercial use, these fuzz-induced imperfections are an important cause for the rejection of laminates.
The use of starch as a sizing agent is well known in the paper industry. In the article "Reduction of Offset Printing Rejects" TAPPI, November 1967 (pp 135A-137A) Richard F. Burtt reports the results of a study initiated to determine causes of rejection of offset printing grade paper. Among his findings Burtt reported that the addition of certain cooked starches via a size press process to a paper sheet containing about 4-5% moisture facilitated the laying down of the surface fibers of offset printing grade paper.
In U.S. Pat. No. 3,210,240, Read et al. teach a process for surface sizing newsprint, newsroto, novel news, directory, and catalog papers. In this method raw, cooked, or modified starch is dispersed in water via use of a wetting agent and compressed air to form a starch foam. The starch foam is subsequently drained of excess water and applied to the newsprint paper at a rate equivalent to 10 to 20 lbs. per ton of air dried paper.
In U.S. Pat. No. 3,639,209, Buckman et al. teach a process for making paper using cationic starch complexes. The authors disclose reacting aqueous starch with a water-soluble cationic polymeric polyelectrolyte to form a cationic starch complex. This starch complex is subsequently added at the fan pump to the furnish in order to improve the linting characteristics of newsprint paper.
In U.S. Pat. No. 3,859,108, Ware et al. teach the use of a cooked flour size (containing both the protein and the starch fractions of the flour) to seal the surface and/or body of paper or paperboard. This treatment improved the internal fiber bonding and laying of the paper's surface fibers.
In British Patent No. 1,601,282, a method for processing paper fiber webs with starch is disclosed. This method requires the heating of a starch solution almost to gelatinization of the starch particles after application of the solution to the paper.
In Canadian Patent No. 848,397, an apparatus for coating newsprint paper with either hydroxyethylated starch, modified starch, various proteins, melamine formaldehyde, urea formaldehyde, sodium alginate, carboxymethyl cellulose, or carboxyethyl cellulose is described. When used in offset lithographic printing the coated newsprint paper produced less lint than uncoated newsprint paper.
In addition to applying a variety of surface sizes to paper, the paper industry has tried other methods of addressing its fuzz problem, including varying the composition and refining level of the paper pulp and vacuuming the paper. Although each of these attempts have met with varying degrees of success, fuzz still remains an important problem in the industry.
Therefore, it is the object of this invention to provide an effective and economical method for preventing fuzz formation in the production and subsequent use of saturated kraft paper. Other objects, features, and advantages will be evident from the following disclosures.